--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -2805,23 +2805,27 @@ nsWindow::OnButtonReleaseEvent(GdkEventB
     WidgetMouseEvent event(true, eMouseUp, this,
                            WidgetMouseEvent::eReal);
     event.button = domButton;
     InitButtonEvent(event, aEvent);
     gdouble pressure = 0;
     gdk_event_get_axis ((GdkEvent*)aEvent, GDK_AXIS_PRESSURE, &pressure);
     event.pressure = pressure ? pressure : mLastMotionPressure;
 
+    // The mRefPoint is manipulated in DispatchInputEvent, we're saving it
+    // to use it for the doubleclick position check.
+    LayoutDeviceIntPoint pos = event.mRefPoint;
+
     nsEventStatus eventStatus = DispatchInputEvent(&event);
 
     bool defaultPrevented = (eventStatus == nsEventStatus_eConsumeNoDefault);
     // Check if mouse position in titlebar and doubleclick happened to
     // trigger restore/maximize.
-    LayoutDeviceIntPoint pos = event.mRefPoint;
     if (!defaultPrevented
+             && mIsCSDEnabled
              && event.button == WidgetMouseEvent::eLeftButton
              && event.mClickCount == 2
              && mDraggableRegion.Contains(pos.x, pos.y)) {
 
         if (mSizeState == nsSizeMode_Maximized) {
             SetSizeMode(nsSizeMode_Normal);
         } else {
             SetSizeMode(nsSizeMode_Maximized);